When Jim Faust looks at radon data for Idaho, he picks Kootenai County as one of the areas to increase awareness.

Faust, radon program manager for the Idaho Department of Health and Welfare, says that's because this area has among the highest levels of the radioactive, naturally occurring, colorless, odorless and tasteless gas in the country.

Results in area cities in the past 15 years have ranged from 51 to 68 percent of the homes tested as having high amounts (4 picocuries per liter or higher) as defined by the U.S. Environmental Protection Agency, according to IDHW.

"It's a very serious issue in Kootenai County," said Faust, adding that exposure to high amounts of radon is the second-leading cause of lung cancer behind smoking.

The IDHW started collecting radon data 15 years ago, but about 80 percent of the test results are from the past two or three years as the word has spread about the gas.

"Since we've found such high levels of radon throughout Kootenai County, we've focused more and more efforts there to get the word out to people," Faust said.

Faust said a postcard has been or will be sent by IDHW to residents in 12 counties, including every homeowner in Kootenai County, asking them to voluntarily test for radon.

"We really don't know exactly why Kootenai County has such high levels," Faust said. "What we're trying to do is get the word out about exposure to high radon levels and ask people to test their homes."

Radon invades homes and buildings from the soil through crawlspaces, foundation cracks and openings. The highest levels are found in winter when homes are closed tight. That makes it the best time to test for the gas, Faust said.

Nearly 40 percent of the homes tested for radon in Idaho have high levels, Faust said.

"Radon is definitely a big problem because it's so prevalent," he said. "The good news is that it is a fixable problem. Every home in Idaho should be tested so you can protect yourself and your family."

The EPA estimates about 21,000 deaths in the United States each year are caused by exposure to radon.

The only way to know if your home has high levels of radon is to test for it. Test kits are $9.95 and are available at www.radonidaho.org. The kit includes the test with easy-to-follow instructions, and the shipping costs and lab analysis are included in the price. You can also call the Idaho CareLine by dialing 2-1-1 to order the kit. If your test results show your home to have high levels, there are ways to reduce it. More information is available at www.epa.gov/radon/pubs/consguid.html and www.radonidaho.org.

Faust said if a home has a high level of radon, the next step depends on the homeowner.

"Many homeowners do absolutely nothing about the high radon levels in their home," he said. "Other homeowners fix or mitigate their home themselves, which costs $500. Still other homeowners have a mitigation company come in and mitigate their home. Mitigation companies guarantee below 2 pCi./L when they fix a house."

Most systems installed by a mitigation company range from $1,800 to $2,500, depending on the home.

Faust said the top reason people do not test their home is because they don't want to know the result. The No. 2 reason is the cost.

"Women will usually order a test kit to protect their children/family," Faust said. "Men want to ignore it, kinda like not going to a doctor."

Faust said radon testing is not a requirement of the home inspection process when homes are either purchased or sold, but it's a good idea and some states have that requirement.

"Many times people who move here are amazed that Idaho does not have that requirement," Faust said.

Monte Hilding, owner of Premier Basement Systems, a Post Falls firm which tests and mitigates radon, said the call to test is important but not cause to panic.

"If radon levels are high, that doesn't automatically mean that you'll get sick," Hilding said. "You have time to start your investigation."

Amounts of radon can vary greatly, depending on the time of year. Hilding said his home tested for 1.2 pCi/L during the summer and 97 during the winter.

"My average was in the 40s, so I still put in a system," he said.

Hilding said it varies whether a homeowner decides to take action if the result is high.

"It's a matter of what your risk tolerance is," he said.

Hilding said there's no guideline on how likely a person is to be affected by high levels of radon.

"The EPA knows it's all about physiology," he said. "You can be exposed to high amounts and never be affected."

IDHW officials said radon needs to be addressed at the local, not state level, because the amounts vary across the state. Therefore, building codes need to be addressed at a local level.

The state works with builders, local government leaders, inspectors and real estate agents to educate them about radon.

Dave Gerard, owner of the Advanced Radon Technologies testing and mitigation firm, said it's not uncommon for homes in this area to have test results between 100 to 300 pCi/L. He believes geology, including conditions caused by the Missoula Floods, are what makes this area prone to radon.

Gerard believes there will be more of an emphasis on radon testing with home inspections in Idaho in the next few years. He has watched that happen in other areas, including Portland, Ore., where he has done testing.

Real estate transactions, he said, will lead to the most awareness about radon.

"It will become part of the real estate transaction just like inspections did," he said. "Portland will be a perfect template for what will happen here."

Radon test results

Here are the number of homes tested in Kootenai County cities in the past 15 years through July 2014 and the percentage of those that tested high for radon (at least 4 picocuries per liter):

City/No. of tests/Percentage with high results

Rathdrum: 392 68.1

Hayden: 655 59.1

Post Falls: 862 68.1

Coeur d'Alene (83814): 605 51

Coeur d'Alene (83815): 842 63.7

SOURCE: Idaho Department of Health and Welfare